Track type work machines are in widespread use in construction, mining, forestry, and similar industries. In particular, bulldozers, cranes and pavers are commonly seen track type work machines along roads, freeways and at construction sites. “Tracks” rather than wheels are typically used on work machines operating in environments where creating sufficient traction with conventional tires is problematic or impossible. Rather than rolling across a work surface on wheels, track type work machines utilize one or more tracks extending about a plurality of rolling elements. Such tracks are typically made up of a loop of coupled metal links having outer sides that engage the ground or work surface, and inner sides travelling about the rolling elements, which can include various drive rollers, support rollers, tensioners and “idlers.”
An idler in a track type work machine is a rolling element that passively rolls against the inner side of the track, and can have a plurality of teeth that engage against the bushings that join the track links as they roll about the same. The idler is typically positioned at an opposite end of the track roller frame to a drive wheel or sprocket, and supports that end of the track during operation. Rollers are typically positioned between the idler and the sprocket, and support the inner side of the track opposite the ground.
Over the course of work machine operation, the various moving parts of the track assembly can undergo significant wear. The track links, rollers, idlers and drive sprockets can all experience wear from the nearly constant metal-to-metal contact. For example, the idler can include grooves or pockets separating the teeth. A phenomenon known in the art as “tooth root wear” describes deepening of these pockets over time due to repetitive engagement and disengagement with the track, which in turn wears due to its corresponding engagement against the idler. A horizontal plane, located at the bottom of the idler, and intersecting bushings in the track can be defined as the idler plane. As the idler and bushings wear, the idler plane can actually migrate. The rollers will also tend to wear down as they operate against the track links over time. The “roller plane” may be thought of as a horizontal plane located at the bottom of the rollers, and intersecting bushings in the track. In a manner similar to the idler plane, wear of the track links and rollers can actually cause the roller plane to migrate.
In many common work machines, in which the idlers run on the links, the idlers, rollers and track links have traditionally been made of similar materials, for example steel, and thus the various elements have a tendency to wear at approximately the same rate. Accordingly, the relative distance between the roller plane and idler plane remains roughly the same over the course of many hours of operation. In the past, servicing of the work machine and replacement of the idlers, rollers and in some instances track links would take place at predetermined intervals, based generally on similar wear rates of the same.
In an attempt to prolong the life of certain of the work machine components, in recent years designers have begun to employ rotating bushings connecting side by side track links, and toothed idlers running on the rotating bushings. The wear rate of rotating bushings is relatively slow, as the rotating bushings can roll into and out of engagement with the other components rather than sliding. The rate of migration/translation of the idler plane is a function primarily of tooth root wear and rotating bushing wear, whereas the rate of migration/translation of the roller plane is a function primarily of roller wear and track link wear. Tooth root wear and rotating bushing wear tends to be slower than roller and link wear, and consequently the rate of change in the position of the idler plane tends to be slower than the rate of change in the position of the roller plane.
Where the rate of change in position of the roller plane outpaces the rate of change in the idler plane, the relative separation of the respective planes can change over time. For many work machine operations, it is desirable to maintain the roller plane and idler plane substantially at constant positions relative to one another. For example, if the idler plane lies at an inappropriate position relative to the roller plane, the ride, blade control or work surface finish can be compromised in certain operations.
The present disclosure is directed to one or more of the problems or shortcomings set forth above.